Moving subdomains under main domain

Hi all,

I’ve got a structure like this:

domain.com
-domain.co.uk
-domain.gr

both domain.cp.uk and .gr are alias to domain.com

I’ve got also 3 subdomains:

sub1.domain.com
sub2.domain.com
sub3.domain.com

What I want is to move all 3 subdomains under the domain.com
Is that possible without loosing any data?

The above scenario happened as I migrated initially the subdomains and then the main domain.

Thanks